The S66 Non-Covalent Interactions Benchmark Reconsidered Using Explicitly Correlated Methods Near the Basis Set Limit

The S66 benchmark for non-covalent interactions has been re-evaluated using explicitly correlated methods with basis sets near the one-particle basis set limit. It is found that post-MP2 'high-level corrections' are treated adequately well using a combination of CCSD(F12*) with (aug-) cc-pVTZ-F12 basis sets on the one hand, and (T) extrapolated from conventional CCSD(T)/ heavy-aug-cc-pV{D, T} Z on the other hand. Implications for earlier benchmarks on the larger S66 x 8 problem set in particular, and for accurate calculations on non-covalent interactions in general, are discussed. At a slight cost in accuracy, (T) can be considerably accelerated by using sano-V{D, T} Zthorn basis sets, whereas half-counterpoise CCSD (F12*)(T)/cc-pVDZ-F12 offers the best compromise between accuracy and computational cost.